In a service operation such as pressure testing of pipe joints and their threaded connections as the pipe string is being assembled and lowered into a well, it is typical practice to position a hydraulic test tool having pack-off devices in the interior of pipe so that fluid under pressure can be used to detect leaks or other defects. In general it is necessary to anchor the test tool to prevent downward movement during the testing operation. The most common type of anchor or slip assembly that has been used in the past has a number of shortcomings. For example the expander cone that is used to expand the slip elements is mounted on a central rod that extends through the slip elements. Due to size constraints imposed by the relatively small internal diameter of the tubing being tested, the presence of the rod reduces the transverse dimensions of the slip elements and thereby reduces their strength and ruggedness. Another problem with prior devices has been due to the fact that the control mechanism which is manipulated to enable setting and release of the slip elements has been exposed on the exterior of the tool, which renders the same subject to malfunction when blocked by debris or the like in the well. Yet another shortcoming of prior devices has been caused by the annular configuration of the slip elements and associated expander cone, which caused the slip elements to be engaged only along an edge thereof in the set position. Such constructions reduced the holding ability of the slip elements under substantial loads, and otherwise reduced the effectiveness of the slip assembly to prevent longitudinal movement in the pipe.
It is the general object of the present invention to provide a new and improved slip assembly of the type described.
Another object of the present invention is to provide a new and improved slip assembly that is constructed and arranged in a manner that enables the use of stronger and more rugged slip elements.
Yet another object of the present invention is to provide a new and improved slip assembly having an internally arranged control means for enabling setting and release of the slip elements.
Still another object of the present invention is to provide a new and improved slip assembly that provides for contact between the expander and the slip elements throughout substantially the entire length of the latter to provide increased anchoring effectiveness.